diff --git a/Package.resolved b/Package.resolved
index 329d16bb..660e69c7 100644
--- a/Package.resolved
+++ b/Package.resolved
@@ -1,5 +1,5 @@
 {
-  "originHash" : "aa0fd2e35b551c5a0558c96a63275f3b05620dac86f000f4bc0c1db36eddbed0",
+  "originHash" : "f375577a6318449b73c9a4adde100413c793e5231ea343b53a0f08072ecaa86b",
   "pins" : [
     {
       "identity" : "darwinprivateframeworks",
@@ -7,7 +7,7 @@
       "location" : "https://github.com/OpenSwiftUIProject/DarwinPrivateFrameworks.git",
       "state" : {
         "branch" : "main",
-        "revision" : "2cec508df7d16801a1bb5b659b906cec465b213e"
+        "revision" : "ad18bd6feaa29e9b138ff7823796c6bc76295fb7"
       }
     },
     {
diff --git a/Sources/OpenGraph/Attribute/Attribute/External.swift b/Sources/OpenGraph/Attribute/Attribute/External.swift
index 417dda14..848f2e0e 100644
--- a/Sources/OpenGraph/Attribute/Attribute/External.swift
+++ b/Sources/OpenGraph/Attribute/Attribute/External.swift
@@ -14,7 +14,9 @@ public struct External<Value> {
 
 extension External: _AttributeBody {
     public static var comparisonMode: OGComparisonMode { ._3 }
+
     public static var flags: OGAttributeTypeFlags { [] }
+
     public static func _update(_: UnsafeMutableRawPointer, attribute _: AnyAttribute) {}
 }
 
diff --git a/Sources/OpenGraph/Attribute/Attribute/Focus.swift b/Sources/OpenGraph/Attribute/Rule/Focus.swift
similarity index 76%
rename from Sources/OpenGraph/Attribute/Attribute/Focus.swift
rename to Sources/OpenGraph/Attribute/Rule/Focus.swift
index c9f89bbf..c3a7ecc8 100644
--- a/Sources/OpenGraph/Attribute/Attribute/Focus.swift
+++ b/Sources/OpenGraph/Attribute/Rule/Focus.swift
@@ -5,7 +5,8 @@
 //  Audited for RELEASE_2021
 //  Status: Complete
 
-public struct Focus<Root, Value> {
+@frozen
+public struct Focus<Root, Value>: Rule, CustomStringConvertible {
     public var root: Attribute<Root>
     public var keyPath: KeyPath<Root, Value>
     
@@ -13,17 +14,10 @@ public struct Focus<Root, Value> {
         self.root = root
         self.keyPath = keyPath
     }
-}
-
-// MARK: - Rule
 
-extension Focus: Rule {
     public var value: Value { root.value[keyPath: keyPath] }
-    public static var flags: OGAttributeTypeFlags { [] }
-}
 
-// MARK: CustomStringConvertible
+    public static var flags: OGAttributeTypeFlags { [] }
 
-extension Focus: CustomStringConvertible {
     public var description: String { "• \(Metadata(Value.self).description)" }
 }
diff --git a/Sources/OpenGraph/Attribute/Rule/Map.swift b/Sources/OpenGraph/Attribute/Rule/Map.swift
new file mode 100644
index 00000000..4965876d
--- /dev/null
+++ b/Sources/OpenGraph/Attribute/Rule/Map.swift
@@ -0,0 +1,25 @@
+//
+//  Map.swift
+//  OpenGraph
+//
+//  Audited for RELEASE_2021
+//  Status: Complete
+
+// MARK: - Map
+
+@frozen
+public struct Map<Source, Value>: Rule, CustomStringConvertible {
+    public var arg: Attribute<Source>
+    public let body: (Source) -> Value
+
+    public init(_ arg: Attribute<Source>, _ body: @escaping (Source) -> Value) {
+        self.arg = arg
+        self.body = body
+    }
+
+    public var value: Value { body(arg.value) }
+
+    public static var flags: OGAttributeTypeFlags { [] }
+
+    public var description: String { "λ \(Value.self)" }
+}
diff --git a/Sources/OpenGraph/Attribute/Rule/AnyRuleContext.swift b/Sources/OpenGraph/Attribute/RuleContext/AnyRuleContext.swift
similarity index 100%
rename from Sources/OpenGraph/Attribute/Rule/AnyRuleContext.swift
rename to Sources/OpenGraph/Attribute/RuleContext/AnyRuleContext.swift
diff --git a/Sources/OpenGraph/Attribute/Rule/RuleContext.swift b/Sources/OpenGraph/Attribute/RuleContext/RuleContext.swift
similarity index 100%
rename from Sources/OpenGraph/Attribute/Rule/RuleContext.swift
rename to Sources/OpenGraph/Attribute/RuleContext/RuleContext.swift
diff --git a/Tests/OpenGraphCompatibilityTests/Attribute/Attribute/AttributeTests.swift b/Tests/OpenGraphCompatibilityTests/Attribute/Attribute/AttributeTests.swift
index d92448e3..176989eb 100644
--- a/Tests/OpenGraphCompatibilityTests/Attribute/Attribute/AttributeTests.swift
+++ b/Tests/OpenGraphCompatibilityTests/Attribute/Attribute/AttributeTests.swift
@@ -1,8 +1,6 @@
 //
 //  AttributeTests.swift
-//
-//
-//
+//  OpenGraphCompatibilityTests
 
 import Testing
 
diff --git a/Tests/OpenGraphCompatibilityTests/Attribute/Attribute/ExternalTests.swift b/Tests/OpenGraphCompatibilityTests/Attribute/Attribute/ExternalTests.swift
index 81e96a31..02229bba 100644
--- a/Tests/OpenGraphCompatibilityTests/Attribute/Attribute/ExternalTests.swift
+++ b/Tests/OpenGraphCompatibilityTests/Attribute/Attribute/ExternalTests.swift
@@ -1,8 +1,6 @@
 //
 //  ExternalTests.swift
-//  
-//
-//
+//  OpenGraphCompatibilityTests
 
 import Testing
 
diff --git a/Tests/OpenGraphCompatibilityTests/Attribute/Attribute/FocusTests.swift b/Tests/OpenGraphCompatibilityTests/Attribute/Attribute/FocusTests.swift
index 084e6e81..a138b9c5 100644
--- a/Tests/OpenGraphCompatibilityTests/Attribute/Attribute/FocusTests.swift
+++ b/Tests/OpenGraphCompatibilityTests/Attribute/Attribute/FocusTests.swift
@@ -1,8 +1,6 @@
 //
 //  FocusTests.swift
-//  
-//
-//
+//  OpenGraphCompatibilityTests
 
 import Testing
 
diff --git a/Tests/OpenGraphCompatibilityTests/Attribute/Indirect/IndirectAttributeTests.swift b/Tests/OpenGraphCompatibilityTests/Attribute/Indirect/IndirectAttributeTests.swift
index b92f540a..25be0440 100644
--- a/Tests/OpenGraphCompatibilityTests/Attribute/Indirect/IndirectAttributeTests.swift
+++ b/Tests/OpenGraphCompatibilityTests/Attribute/Indirect/IndirectAttributeTests.swift
@@ -1,9 +1,6 @@
 //
 //  IndirectAttributeTests.swift
-//
-//
-//  Created by Kyle on 2024/3/3.
-//
+//  OpenGraphCompatibilityTests
 
 import Testing
 
diff --git a/Tests/OpenGraphCompatibilityTests/Attribute/Optional/AnyOptionalAttributeTests.swift b/Tests/OpenGraphCompatibilityTests/Attribute/Optional/AnyOptionalAttributeTests.swift
index 599f493e..c7ee8b98 100644
--- a/Tests/OpenGraphCompatibilityTests/Attribute/Optional/AnyOptionalAttributeTests.swift
+++ b/Tests/OpenGraphCompatibilityTests/Attribute/Optional/AnyOptionalAttributeTests.swift
@@ -1,9 +1,6 @@
 //
 //  AnyOptionalAttributeTests.swift
-//
-//
-//  Created by Kyle on 2024/3/3.
-//
+//  OpenGraphCompatibilityTests
 
 import Testing
 
diff --git a/Tests/OpenGraphCompatibilityTests/Attribute/Optional/OptionalAttributeTests.swift b/Tests/OpenGraphCompatibilityTests/Attribute/Optional/OptionalAttributeTests.swift
index 81ea2f82..f5adf8b6 100644
--- a/Tests/OpenGraphCompatibilityTests/Attribute/Optional/OptionalAttributeTests.swift
+++ b/Tests/OpenGraphCompatibilityTests/Attribute/Optional/OptionalAttributeTests.swift
@@ -1,9 +1,6 @@
 //
 //  OptionalAttributeTests.swift
-//
-//
-//  Created by Kyle on 2024/3/3.
-//
+//  OpenGraphCompatibilityTests
 
 import Testing
 
diff --git a/Tests/OpenGraphCompatibilityTests/Attribute/Rule/MapTests.swift b/Tests/OpenGraphCompatibilityTests/Attribute/Rule/MapTests.swift
new file mode 100644
index 00000000..3f9238b2
--- /dev/null
+++ b/Tests/OpenGraphCompatibilityTests/Attribute/Rule/MapTests.swift
@@ -0,0 +1,26 @@
+//
+//  MapTests.swift
+//  OpenGraphCompatibilityTests
+
+import Testing
+
+@Suite(.disabled(if: !compatibilityTestEnabled))
+final class MapTests: AttributeTestBase {
+    @Test
+    func description() throws {
+        let map = Map(.init(value: 2)) { $0.description }
+        let map2 = Map(.init(value: 1)) { $0 + 2 }
+
+        #expect(map.description == "λ String")
+        #expect(map2.description == "λ Int")
+    }
+
+    @Test
+    func value() throws {
+        let map = Map(.init(value: 2)) { $0.description }
+        let map2 = Map(.init(value: 1)) { $0 + 2 }
+
+        #expect(map.value == "2")
+        #expect(map2.value == 3)
+    }
+}
diff --git a/Tests/OpenGraphCompatibilityTests/Attribute/Rule/RuleTests.swift b/Tests/OpenGraphCompatibilityTests/Attribute/Rule/RuleTests.swift
index 65785aca..2e27ac9d 100644
--- a/Tests/OpenGraphCompatibilityTests/Attribute/Rule/RuleTests.swift
+++ b/Tests/OpenGraphCompatibilityTests/Attribute/Rule/RuleTests.swift
@@ -1,8 +1,6 @@
 //
 //  RuleTests.swift
-//
-//
-//
+//  OpenGraphCompatibilityTests
 
 import Testing
 
diff --git a/Tests/OpenGraphCompatibilityTests/Attribute/Weak/OGWeakAttributeTests.swift b/Tests/OpenGraphCompatibilityTests/Attribute/Weak/OGWeakAttributeTests.swift
index c19cf81d..30d5cfc8 100644
--- a/Tests/OpenGraphCompatibilityTests/Attribute/Weak/OGWeakAttributeTests.swift
+++ b/Tests/OpenGraphCompatibilityTests/Attribute/Weak/OGWeakAttributeTests.swift
@@ -1,9 +1,6 @@
 //
 //  AnyWeakAttributeTests.swift
-//
-//
-//  Created by Kyle on 2024/3/4.
-//
+//  OpenGraphCompatibilityTests
 
 import Testing
 
diff --git a/Tests/OpenGraphCompatibilityTests/Attribute/Weak/WeakAttributeTests.swift b/Tests/OpenGraphCompatibilityTests/Attribute/Weak/WeakAttributeTests.swift
index a34735ad..8f431f33 100644
--- a/Tests/OpenGraphCompatibilityTests/Attribute/Weak/WeakAttributeTests.swift
+++ b/Tests/OpenGraphCompatibilityTests/Attribute/Weak/WeakAttributeTests.swift
@@ -1,9 +1,6 @@
 //
 //  WeakAttributeTests.swift
-//  
-//
-//  Created by Kyle on 2024/3/3.
-//
+//  OpenGraphCompatibilityTests
 
 import Testing